How Rooibos Is Processed

Rooibos is harvested once a year, from summer into early autumn, and the cut is deliberately high. Whole branches are taken about 50 centimetres above the ground¹ (roughly 20 inches), which leaves the bush enough standing frame to regrow for the following season. It is a single annual window for the whole country's cup: South Africa produces more than 20,000 tonnes of rooibos a year¹ (roughly 22,000 US tons) from the Cederberg and its neighbouring districts, centred on Clanwilliam.

1. South African Rooibos Council, Rooibos harvest season in Clanwilliam

At the yard, the sheaves go through a rotary cutter, which chops branch, leaf and stem together into uniform lengths of 1.5 to 5 millimetres¹. The same blades also bruise the plant. The full sequence of yard operations, cut through heap through dry, is set out in how the harvest is processed.

1. South African Rooibos Council, Rooibos harvest season in Clanwilliam

The cut, bruised leaf is spread in the open drying yards, watered, and left in heaps to sweat. Watering typically begins in mid-afternoon³, after which the heaps are turned and aired several times before evening and then roughly every four hours through the night. The heap is left to sweat for 10 to 14 hours at 34 to 38 degrees Celsius¹ (about 93 to 100 Fahrenheit).

3. Roemer's Grinding Works, Rooibos Processing: From Field to Cup
1. South African Rooibos Council, Rooibos harvest season in Clanwilliam

Work resumes around dawn. The fermented rooibos, deep amber now rather than green, is pressed, traditionally by driving a tractor over the rows, so its own coloured liquid runs back through the pile³, then spread thin across the yard to dry in the open Cederberg sun. Workers reposition it through the day as the surface dries unevenly. Drying runs about nine hours³ and is judged finished once moisture content drops below roughly 8.5 percent.

3. Roemer's Grinding Works, Rooibos Processing: From Field to Cup

Once dry, one harvest becomes many products. The South African Rooibos Council states that rooibos is graded on colour, flavour, cut length and aroma⁴, and the sorting that makes those judgements possible is mechanical: the dried leaf passes through a bank of sieves, rolling, vibrating, maxi and indent types², separating the batch by size and quality.

4. South African Rooibos Council, Frequently Asked Questions
2. Carmién Tea International, Rooibos Production and Processing

What comes out is sorted into four quality tiers⁷:

7. Roemer's Grinding Works, Understanding Rooibos Flavour Profile, Cut Grades & Quality

What sieves out as the very finest material becomes rooibos powder and micro powder⁵, sold for espresso-style blends, instant granulates, smoothies and baking rather than steeped as loose leaf. The tier and cut a batch lands in, and what that means for a buyer, is covered in full in grading and cuts.

5. Carmién Tea International, Rooibos Grades and Cuts

Researchers at the Agricultural Research Council's Infruitec-Nietvoorbij campus and Stellenbosch University's Department of Food Science built a rooibos sensory wheel⁸ from tasting-panel data, first developed in 2011 and revised in 2017 and 2021, which gives the industry a shared vocabulary for the tea's flavours and mouthfeel. The food scientist Elizabeth "Lizette" Joubert was on the founding team and has kept teaching graders to use it⁹.

8. Koch, Muller, Joubert, van der Rijst & Næs, Sensory characterization of rooibos tea and the development of a rooibos sensory wheel and lexicon, Food Research International (2012)
9. Carmién Tea, The Rooibos Sensory Wheel

After grading and sieving, every batch goes through steam pasteurisation, exposed to steam at around 160 degrees Celsius² (320 Fahrenheit) for 90 seconds, then screened directly for Salmonella, E. coli and other microbes at facilities holding FSSC22000 and ISO 9001 food-safety certification¹⁰.

2. Carmién Tea International, Rooibos Production and Processing
10. Klipopmekaar, Rooibos Tea Processing

A 2014 peer-reviewed review by food scientists at Stellenbosch University found that rooibos "naturally contains a high microbial load,"¹¹ and that "the presence of Salmonella in Rooibos is poorly understood," a gap the review itself called on the industry to close. A single 2013 recall of a Canadian rooibos blend for possible Salmonella is set out in full in pasteurisation and Salmonella safety.

11. Gouws, P., Hartel, T., van Wyk, R., The influence of processing on the microbial risk associated with Rooibos (Aspalathus linearis) tea, Journal of the Science of Food and Agriculture 94(15):3069-3078 (2014)

Rooibos makes none of the liver-toxin family called pyrrolizidine alkaloids on its own. Chemists have traced the major source of pyrrolizidine contamination in rooibos tea¹² to a Cape weed, Senecio angustifolius, known as bitterbos, which resembles rooibos closely enough to be cut and dried along with the harvest by mistake. The EU sets rooibos, with chamomile, peppermint and four other herbs, a higher pyrrolizidine ceiling¹³ than the general herbal-tea limit. On the more familiar worry of pesticide spray, a 2022 South African study screening 100 retail rooibos products¹⁴ found residues of the 13 pesticides tested in only one, below EU limits. The weed, its identification, and how a yard keeps it out are covered in full in the lookalike weed problem.

12. Van Wyk, B.-E., Stander, M.A., Long, H.S., Senecio angustifolius as the major source of pyrrolizidine alkaloid contamination of rooibos tea (Aspalathus linearis), South African Journal of Botany 110 (2017): 124-131
13. Commission Regulation (EU) 2020/2040 amending Regulation (EC) No 1881/2006 as regards maximum levels of pyrrolizidine alkaloids, Annex (retained EU law text)
14. Areo, O.M., Olowoyo, J.O., Sethoga, L.S., Adebo, O.A., Njobeh, P.B., Determination of pesticide residues in rooibos (Aspalathus linearis) teas in South Africa, Toxicology Reports (2022)

Not all processed rooibos ends as leaf. Extract is a separate product, made by soaking purified leaf and stem in hot water, filtering out the solids, concentrating what remains, and spray-drying it¹⁵ into a fine, water-soluble powder. It comes in red, from fermented and oxidised leaf, and green, dried quickly to skip oxidation and marketed for higher retained aspalathin, which is the same divide the leaf itself has and is set out in green versus red rooibos. From there it goes into flavoured water, energy drinks, baked goods, dairy, sauces, anti-ageing creams, soothing balms and supplement capsules.

15. South African Rooibos Council, Rooibos Extracts

A 2021 Stellenbosch study found that spray-dried green rooibos iced-tea powder formulations lost between roughly 9.7 percent and 90.3 percent of their aspalathin over twelve months at 40 Celsius¹⁶ (104F), depending on formulation. The engineering of extract powders is given in full in how rooibos becomes an extract.

16. Human, de Beer, Muller et al., Shelf-Life Stability of Ready-to-Use Green Rooibos Iced Tea Powder, Molecules 26(17):5260 (2021)